Control for automatic transmission

ABSTRACT

In an electrical control for an automatic transmission, including a throttle position signal generator and having vehicle speed as well as throttle position as input signals and an optimum selection of gear range as an output, the improvement wherein the throttle position signal generator comprises a magnet operatively connected to a throttle valve, a plurality of magnetically energized switches connected with a circuit including resistors and a source of electric energy for generating a stepped throttle position signal voltage.

. [22] Filed:

United states Patent Araiet al. I

1541 CONTROL FOR AUTOMATIC TRANSMISSION [72] Inventors: Hiroshi Arai; Takakazu Morl, both of Toyota, Japan [73] Assignee: Toyota Jidosha Kogyo- Kabushiki Kaisha, ToyOta-shi, Japan Oct. 12, 1970 21 App]. No.: 80,116

[30] Foreign Application Priority Data opt-20, 1969 Japan "4418-3759 1 s21 U.S. c| ..74/866, 307/116 [51] Int. Cl. B60k 21/00, HOlh 36/02 [58] Field of Search ..74/866; 307/116 [56] References Cited UNITED STATES PATENTS 1/1959 Gill, Jr ..74/866 X [151 3,707,097 [451 Dec. 26, 1972 Schmidt et al ..74/866 X Primary Examiner-Arthur T. McKeon Attorney-Stevens, Davis, Miller & Mosher $7 ABSTRACT,

In an electrical control for an automatic transmission, including a throttle position signal generator-and having vehicle speed as well as throttle position as input signals and an optimum selection of gear range as an output, the improvement wherein the throttle position signal generator comprises a magnet operatively connected to a throttle valve, a plurality of magnetically energized switches connected with a circuit including resistors and a source of electric energy for generating a stepped throttle position signal voltage.

9 Claims, 12 Drawing Figures Fwl PATENTEBBEE 25 um SHEET 3- OF T KSEG MQQQ .QI 1 K 5595 mmQQ him PATENTED M826 m2 SHEET 5 [1F 7 mm mm 9 mm R m an DQ mi 7 4 55mg 7 7 Kass 7 MT MN "I W n Wm k 7 3M v? m vb Q N QEQSQQ Ni w l I I I I l I. I. I l I .I wwm m q m N i N Ti f fmvwfi 51E E1 PATENTED DEC 2 5 I922 SHEET 5 [1F 7 SHEET 7 OF T PATENTED DEC 26 m2 1 CONTROL FOR AUTOMATIC TRANSMISSION BACKGROUND or THE INVENTION 1. Field of the Invention This invention relates to acontrol for an automatic transmission, and particularly to an electrical control for an automatic transmission of the kind used in automotive vehicles having multiple forward speed ranges, a neutral range, and a reverse range.

2. Description of the Prior Art To control an automatic transmission having multiple forward speed ranges, a neutral range, and a reverse range, at least three basic control signals are necessary. These signals are: an engine operated parameter signal, a vehicle speed signal, and a manualgear range selector signal. Most commonly, the engine operated parameter signal is represented by a throttle position signal, and the vehicle speed signal is represented by a transmissionoutput shaft speed signal. When a manual gear range selector which selects one range out of several ranges including a forward range, a neutral range, and a reverserange is set to the forward range by a driver, forward gear range shifts of an automatic transmission are controlled by the throttle position signal and the vehicle speed signal according to a predetermined shift pattern which is described in terms of throttle position and vehicle speed.

When a hydraulic medium is used exclusively, the control system becomes very complex. Therefore, efforts are continuously being made to replace signal generating and processing means of the control system, which is operated hydraulically, with electrically operated means to make the control system simpler. This electrically operated means is hereinafter called an electrical control circuit.

The priorart electrical control circuit utilizes a potentiometer or a multicontact switch, each linked with an engine throttle valve and also connected with a battery or another kind of electric energy generator and resistors, if necessary, to produce a voltage which corresponds to throttle. position and is, therefore, the throttle position signal. This voltage is, in general,

-. called a throttle voltage.

However, the potentiometer and the multicontact switch have two disadvantages: one is that they lack durability due to friction contact between the moving part linked with the engine throttle valve and the stationary part, and the other is that they often produce distorted signals caused by vibrations at contact points, which are transmitted from the vehicle body or the engine.

When the potentiometer is utilized, the throttle voltage changes continuously as the throttle position changes. Usually a relationship between the throttle voltage and the throttle position is linear. However, when the multicontact switch is utilized, the throttle voltage changes discontinuously as the throttle position changes, and is expressed by a stepped line in relation downshift line which correspond to upshifts and downshifts between the same adjacent gear ranges. Also in the same diagram shift lines are continuously smooth sloped lines, usually sloped straight lines, in their major portions or in all portions when the potentiometer is used, but the shift lines are stepped lines when the multicontact switch is used. Further in the same diagram, a space or spaces must be provided between the upshift line and the downshift line corresponding thereto to provide hysteresis in the electrical control circuit for the prevention of oscillation between the gear ranges. When the potentiometer is utilized, if the space along the vehicle speed axis between the upshift line and the downshift line corresponding thereto is provided, the space along the throttleposition axis between the twois inherently provided, because the shift lines are sloped. This means that no oscillation occurs when shifts occur due to a change of the position of a point representing the condition of vehicle speed and throttle position in the shift pattern diagram along the vehicle speed axis or the throttle position axis or both. However, when the multicontact switch is utilized, even if the space along the vehicle speed axis between the upshift line and the downshift line corresponding thereto is provided, the space along the throttle position axis between the two is not automatically provided, because the shift lines are stepped lines. Therefore, when the multicontact switch is utilized, the electrical control circuit which provides the space along the throttle position axis between the upshift line and the downshift line corresponding thereto as well as the space along the vehicle speed axis between the two becomes more complicated than the electrical control circuit which provides the space only along the vehicle speed axisbetween the upshift line and the downshift line corresponding thereto. Therefore, when the multicontact switch is utilized, usually only the space along the vehicle speed axis between the upshift line and the downshift line corresponding thereto is provided to avoid the complexity of the structure and mechanism of the electrical control circuit at the sacrifice of the oscillation between gear ranges at the portions of the shift pattern diagram where no space is provided between the upshift lines and the downshift lines corresponding thereto.

Although the electrical control circuit employing a multicontact switch and providing only the space along the vehicle speed axis has the above-mentioned disadvantage, has a big advantage over the electrical control circuit employing a potentiometer. This advantage is that the structure and mechanism of the former becomes very simple as compared with the latter.

SUMMARY OF THE INVENTION The control for an automatic transmission of this invention utilizes the same structure and mechanism as the control for an automatic transmission (hereinafter called the simple control) which employs a multicontact switch as a distinct part of the throttle position signal generator incorporated in the electrical control circuit of the control and which provides only the space along the vehicle speed axis between the upshift line and the downshift line corresponding thereto in the predetermined shift pattern diagram without providing the space along the throttle position axis between the mechanism among the controlsfor automatic transmissions describedb'elowfi l) onewhich uses a hydraulic mediumexclusively; (2) one'which uses a potentiome ter'asa distinct part of the throttleposition signal generator incorporated in the electrical control circuit i ofthe control and provides the space between the corresponding upshift and downshift lines along the vehicle-speed and throttle position-axes; ("3) one which'uses ajmulticontact switch as a distinct part of thethrottle position signal generator incorporatedin the electrical tion signal generator by the elimination of'direct contact between the moving part linked with the throttle control Scircuit'of the control and provides the space between the corresponding upshift and downshift lines along the vehicle speed and throttle position axes; and

(4). t he simple control beingherein described, except the multijcontact switch which is replaced by a new switch device which is a part-of thisinvention to take advantage of simplicity of the simple control and,

, therefore,'.to take advantage of increased'reliability and reduced production cost as the result of the simplicity.

. The switch device of this'invention comprisesmagnetic means operatively associated with a throttle valve of an engine driving the automatic transmission and a disposed in afspac'ed relationship to'each other and to the j magnetic means. The magnetically energized switch means is energized by the magnetic means to which is a' switch comprising a container usually made of glass, apair-of-metal reeds-disposed 'in'the container in a=confronting manner and having an overlapped portion near the tips thereof with 'a small gap 'therebetween. When the reedfswitch is energized by a magnetic flux formed by-the magnet and passing L plurality. ofmagnetically energized switch means valve and the stationary part of the switch device. l BRIEF: DESCRIPTION OF THE DRAWINGS FIG. 1 is aschematic diagram of a throttle voltage generating circuitof this invention. FIG. 2 is a plan view of a switch device of this inven- FIG. 3aand 3b taken together show a'shape and magnetic poles of a permanent magnet incorporated in the switch device shown in FIG. 2. I Y 'FlG.3bisaviewAofFIG.3a. Y 1 ,1

FIG. 4 is a'diagram showing a relationship between throttle ,voltageE and throttle angle Oobtained from the throttle voltage generating circuit shown in FIG. 1, a component of which is the switch device shown in no.2. g P FIG. 5 is a block diagram of anelectrical control circuit for a three forward speedau'tomatic transmission.

FIG. 6 is a diagram of a vehicle speed signal voltage E, which is produced by a speed sensor connected with terms of throttle voltage versus vehicle speed voltage.

through the reeds, the reeds contact with each other,

. thereby closing the switch. When thereed switch is deenergized, the-reed switch opens dueto the resilient force of .thereeds.

I When the simple control is modified by replacing the multicontact switch of the simple control with the switch device of this invention, the modified simple control has a big-additional advantage while maintaining the advantage of simplicity of the original simple I control. This additional advantage is that the modified simple control has, due to the hysteretic characteristic of the switch device of this invention, the space along the throttle position axis between the corresponding upshift and'downshift lines as well as the space along the vehicle speed axis :between the corresponding upshift and downshift lines, for prevention of oscilla- 'tion" between gear ranges when shifts occur along the throttle position axis as well as the vehicle speed axis.

Another advantage of the modified simple control of Still another advantage of the modified simple conconnected to a torqueconverter 80 to transmit the entrolof this invention is an improvement in the durability of the'switch device'incorporate'd in the throttle'posi- FIG. 8is a diagram of the same shift pattern as shown in FIG. 7, drawn in terms of throttle angle 0 versus vehicle speed.

FIG. 9 is a sectional view of a three forward speed transmission to which the control of this invention applies. I q

FIG. 10 is a schematic diagram of a hydraulic actuating system which applies to the three forward speed transmission.

FIG. 11 is a circuit diagram of a l- 2 shift judge circuit of this invention. i 1

which is described, in detail in a copending US. Pat. ap-' plication Ser. No. 874,934 (filed Nov. 7, 196,9; Inventors: Wakamatsu et al.), assigned to the-same assigneeof this invention Referring to FIG 9 thethree forward speed transmis-' sion illustrated includes an input shaft 81 driven by an engine (not shown in the drawing). The input shaft is gine power to. the torque converter. The torque converter includes a torque converterturbine shaft 82 which transmits the output power of the torque converter operatively to a planetary gear set 50. The-planetary gear set 50 comprises a first sun gearSl, a second sun gear 57, a third sun gear 55, first planetary gears 52, second planetary gears 54, a carrier 53, and a transmission output shaft 56. The first sun gear 51 and the second sun gear 57 are disposed opposite to each other to mesh with each other through the first planetary gears 52, and the second planetary gears 54 are integral with the first planetary gears 52 so as to mesh with the third sun gear 55. The transmission output shaft 56 is operatively connected to the vehicle wheels for driving the vehicle. 7

A front clutch 20, a rear clutch 30, a front brake 60, and a rear brake 40 are provided for conditioning the planetary gear set for the change in speed ration.

The change of the gear ranges can be attained by actuating the clutches and brakes in the following manner: I

Reverse (R): Rear clutch 30 and Rear brake 40 actuated First gear range (L); Front clutch and Rear brake 40 actuated Second gear range (DL): Front clutch 20 and Front brake 60.actuated Third gear range (DH Front clutch 20 and Rear c|utch actuated (note: Clutches or brakes not mentioned in each of gear ranges are not actuated.)

The front clutch 20 is composed of a clutch drum 21 connected integrally with the torque converter turbine shaft 82, a multiple disc clutch 22, a clutch piston 23, a spring plate 24, and a clutch shaft 25. When an actuating hydraulic pressure is applied thereto, the front clutch 20 acts to couple the torque converter turbine shaft 82 and the clutch shaft 25.

The rear clutch 30 is composed of a clutch shaft connected'integrally with the clutch drum 21 of the front clutch 20, a clutch drum 31, a multiple disc clutch 32, a clutch piston 33, and a spring plate 34. When an actuating hydraulic pressure is applied thereto, the rear clutch 30 acts to couple the clutch drum 2] and the clutch drum 31.

i As shown in FIG. 10, the'front brake 60 is composed of a brake piston 61, a brake link 62, a brake band 63, a return spring 64, and a brake cylinder 65. When an actuating hydraulic pressure is applied thereto, the brake band 63 is actuated to ground the second sun gear 57.

Also as shown in FIG. 10, the rear brake 40 is composed of a brake piston 41, a brake link 42, a brake band 43, a return spring 44, and a'brak'e cylinder 45. When an actuating hydraulic pressure is' applied thereto, the brake band 43 is actuated to ground the carrier 53. v

.A hydraulic actuating system preferably used in the automatic transmission of the kind described above is shown in FIG. 10.

Referring to FIG. 10 the hydraulic actuating system comprises a hydraulic pressure source 250, a hydraulic actuating circuit 230, the front clutch 20, the rear clutch 30, the front brake 60, and the rear brake 40.

The hydraulic pressure source 250 includes a hydraulic pump 17, an oil filter 259, an oil pan 258, a pressure regulating valve 256, a pressure control valve 252, arelief valve 253, and an oil cooler 254. The hydraulic pressure source 250 functions to supply oil under pressure to the torque converter 80, to the planetary gear set 50 for lubricating the same, and to the hydraulic actuating circuit 230. 1

The hydraulic actuating circuit 230 includes a manual valve 1260, a first shift valve 1270, a second shift valve 1290, and check valves 291 and 295. The

manual valve 1260 is composed of a valve spool 1262 and a valve casing 1261. The valve spool 1262 is adapted for interlocking operations with a controllever (not shown in the drawing) disposed adjacent to the drivers seat so that it takes a corresponding position in response to urging of the control lever to one of the P (parking), R (reverse), N (neutral), D (drive), 2D (second and first gear range), and L (first gear range) positions. Symbols P, R, N', D, 2D, and L shown in FIG. 10 represent the corresponding positions of the valve spool 1262 which is moved in relation therewith. FIG. 10 shows the hydraulic actuating circuit in a position of the reverse, wherein pressured fluid from an oil passage 221 actuates the rear clutch 30 and the rear brake 40. The oil passage 221 leads to the manual valve 1260 and is divided into two branches. An oil passage 1222 leads out of the manual valve 1260 and is divided into two branch passages one of which communicates with the first shift valve 1270, while the other communicates with the front clutch 20. An oil passage 1223 leads out of the first shift valve 1270 and is divided into two branch passages, one of which communicates directly with the brake cylinder 65 of the front brake 60, while the other communicates with the second shift valve 1290. An oil passage 1301 leads out of the second shift valve 1290 and is divided into two branch passages, one of which communicates with the rear clutch 30, while the other communicates with the brake cylinder 65 of the front brake 60. An oil passage 1227 leads out of the first shift valve 1270 and communicates with the brake cylinder 45 of the rear brake 40. The first shift valve 1270 is provided-with a valve spool 1272 which is associated with a l 2 shift solenoid 1280. (The phrase I 2 shift is defined hereinafter.) The second shift valve 1290 is provided with a valve spool 1292 which is associated with a 2 3 shift solenoid 1300. (The phrase 2 3 shift is also defined hereinafter.) Combinations of energization of these two solenoids in the manner described below accomplish the change gear ranges by activating the clutches and brakes in the previously described manner:

First gear range: no solenoid energized Second gear range: Solenoid 1280 energized Third gear range: Solenoid 1280 and 1300 energized (Solenoids not mentioned in each above gear range are not energized).

Energization of the solenoid 1280 urges the valve spool 1272 of the first shift valve 1270 leftwards in FIG. 10 to thereby provide the communication between the oil passages 1222 and 1223. De-energization of the solenoid 1280 brings the valve spool 1272 back to the rightward position shown in FIG. 10 to thereby cut off the communication between the oil passages 1222 and 1223 and to establish the communication between the oil passages 1222 and 1227. The second shift valve 1290 cuts off the communication between the oil passages 1223 and 1301 when its valve spool 1292 is in the position illustrated. Energization of the solenoid 1300 urges the valve spool 1292 leftwards in FIG. 10 to provide the communication between the oil passages 1223 and 1301.

The electrical control circuit of this invention (the electrical control circuit of the modified simple control) is next described below.

First of all, means for generating thethrottle position position signal generator; or a throttlei voltage generatingcircuitis'described below.

f The throttlevoltage generating circuit of this invention"comprisefs theiswitch device of this invention;

ln' carrying out this invention various types of switch devices, such as a rotary type (a type in whichthe permanent'magnet rotatesas a-'throttle-valve rotates), or a sliding'ty'pe '(atype in which the permanent magnet i signal (thelthrottle voltage)-whi ch is calleda throttle V slides as'a'fthrottle valve-rotates) can be utilized. The

specific embodiment described hereinis a switch Sidn.

1 :Examples-of reed switches which can be used in this invention-are those manufactured byWestern Electric device foffa rotary-g type 'with'four. reed switches, designed to: apply toa three forward'speed transmis- 5 Co., -U.S.A., having code numbers 224A, 237B and G29, although in this particular embodiment Fujitsu reed: switches manufactured by Fujitsu Co., Japan are utilized. 1

Referring to'FlG. l the throttle voltage generating H circuit illustrated comprises: a' battery '1 whose electromotive force is'E and whoseneg ativeterminal is grounded, apermane'nt magnet 2, (which is drawn by phantom lines) whose magnetic poles and movement are shown by N and S anda two-head arrow, respec- A Thes'witch device as shown'in FIG. 2 comprises a case 18 made of plastic in-which the'reed switches 3, 4;

I 5, and 6a're mounted,'and a rotor 9 which'is located insidethe case 8=and connecte'd'with'an engine throttle valve (notshown in the drawing) by means of an arm Ipasseseach switch. The switches are de-energized I when the magnetic flux is sufficiently reduced'by the movement ofthe magnet away from the switches.

Still referringto FIG. 2 a situation in which a throttle angle,'which is'an angle indicating throttle position, is consecutively increased from the fully closed throttle position is first'considered below.

The reed switch 3 is located in a position where its electric circuit is closed when a throttle angle measured fully closed throttle position) by depressing an acceler'a'tor pedal but does not reach 0 all reed switches are off and, therefore, the throttle voltage measured at the voltage output terminal 7 is 'whereE =.throttle voltage when the throttle angle s increased from zero but is less than 0L 8 When the accelerator pedal is further depressed to obtain a throttle anglebetweenfl and .0 the. reed switch 3 is on and consequently the throttle voltage is where-E throttle voltage'when the throttle angle ,is-increased from an angle smaller than 0, toan ,angle between 0 'and 0,.

Likewise, when the accelerator pedal is, further depressed to obtain throttlev angles between 0,; and 0 between 0 and 0 and between 0 and 0 (the angleof the full throttle position), the reed switches Sand 4 are on, 3, 4, and 5 are on, and 3, 4, 5, and 6 are on, respectively. Consequently, the throttle voltages become respectively v where E throttle voltage when the throttle angle is increased from an anglesmallerthan 0 to an angle between 0 and0 ,v

where E throttle voltage whenthe throttle angle isincreased from an angle smaller than0 to an angle between 0 and 0 t t and t R1 11-f1 1"1" R1'i 2+E+E+7'5+E':

where E throttle voltage when the throttle angle is increased from an angle-smaller than 0 man angle between 0 and 0 A situation in which the throttle angle is consecutively decreased is'nextconsidered. I Even if the throttle-angle is decreased to 0 from 0,, (the full throttle position) by releasing the accelerator pedal, reed switch 6 does not become deenergized due to hysteresis of the reed switch. Only when thethrottle angle becomes a certain fixed angle. smaller than 0 that reed switch 6 will be de-energized. That fixed angle is hereinafter designated as 0 In other words, when the throttle angle is greater than 0 'while it is throttle angle is being decreased from 0 continuously by releasing the accelerator pedal are designated as 0,, 0,,and 0,, respectively. Again in other words, in the range between 0 and 0 between 0, and 0,, between 0,"and 0 and between 0, and zero (the fully closed 9 throttle position) the throttle voltages are E E E and E respectively. The foregoing relationship between the throttle angle and the throttle voltage E is shown in FIG. 4.

- In contrast to the above the throttle voltage generating circuit which replaced the reed switches witha multicontact switch produces the throttle voltages B E E E and E in the ranges between 0 and 6 between 0,, and 0 between 0 and 0 between 6 and 6,,andbetween 8, and zero, respectively, when the throttle angle is consecutively decreased.

Although in this embodiment four reed switches are used, it is clear that more reed switches can be used to get a finer throttle angle-- throttle voltage relationship.

It is also clear that in view of the lack of direct contact between the moving part'(the rotor) linked with thethrottle valve and the stationary part (the case) the durability of the switch device of this invention is highly improved as compared'with that of potentiometers or multicontact switches which have friction contact elements such as sliding contacts or multicontact points, and that the throttle voltage produced by the throttle voltage generating circuit comprising the switch device of this invention is not distorted by disturbances which are caused by vibrations transmitted from the vehicle I body or the engine while the throttle voltage produced by the throttle voltage generators comprising poten- .tiometers or multicontact switches is distorted by the above-mentioned disturbances, since the hysteretic characteristic of the reed switches eliminates the disturbances. I 1

Referring to FIG. 5 the switch device 320 of this invention is, as previously described, a component of the throttle voltage generating circuit 1320 which produces the throttle voltage as shown in FIG. 4.

- The vehicle speed signal is usually represented by the transmission output shaft speed as previously mentioned;

' A speed sensor 310 which detects the speed of the transmission outputshaft is preferably a pulse generator '31l-(as shown in FIG. 9) comprising a toothed member 312 (as shown in FIG 9) driven by the transmission output shaft 56 (shown in FIG. 9) and an adjacent inductor pickup 311 (as shown in FIG. 9) which generates a pulse every time a tooth of the member 312 passes the pickup 311 so that the frequency generated in the pickup 311 is proportional to the transmission output shaft speed. This frequency signal is fed to a frequency converter 1310 which produces an output voltage proportional to the transmission output shaft speed. An example of the thus obtained relationship between the vehicle speed V and the transmission output shaft voltage (vehicle speed voltage E, is shown in FIG. 6. The frequency converter 1310 comprises an amplifier, an amplitude limiter, and a frequency detecting, rectifying, and amplifying circuit. (An Example of such a frequency converter is shown in US. Pat No. 3,332,406,issued to Perry et al. on July 25, 1967.) The frequency signal is first supplied to the amplifier in which the amplitude of the frequency signal is increased. The amplitude limiter limits the amplitude of the signal to a fixed value, and converts the shape of the waveform of the frequency signal into a rectangular waveform, because the rectangular waveform similar to the original signal waveform is maintained even after the frequency signal is amplified. The frequency detecting, rectifying, and amplifying circuit converts the output of the amplitude limiter into a DC. voltage. The amplifier, the amplitude limiter, and, the frequency detecting, rectifying, and amplifying circuit are all of the conventional type.

A 1-2 shift judge circuit 1360 consists of a 1-2 shift comparison circuit 1330 and a 1-2 shift feedback circuit 1340. Similarly, a 2-3 shift judge circuit 1460 consists of a 2-3 shift comparison circuit 1430 and a 2-3 shift feedback circuit 1440. Here l-2 shifts and 2-3 shifts mean shifts between the first gear range and the second gear range, and shifts between the second gear range and the third gear range, respectively. A 1-2 upshift means a shift from the first gear range to the second gear range, and a 1-2 downshift means a shift from the second gear range to the first gear range. Similarly, a 2-3 upshift and a 2-3 downshift mean a shift from the second gear range to the third gear range, and a shift from the third gear range tothe second gear range, respectively.

The throttle voltage E and the vehicle speed voltage E, are suppliedfrom the throttle voltage generating circuit 1320 and'the frequency converter 1310, respectively, to the judge circuits 1360 and 1460.

The l-2 shift judge circuit 1360 has a structure as shown in FIG. 11.

Referring to FIG. 11 the 1-2 shift comparison circuit 1330 includes a comparator 3350f the kind sold by the trade code number of SN727 ION which is described in The Integrated Circuit Catalog for Design Engineers," First Edition by Texas Instruments Co., USA. or pipe 71 by Nippon Electric Co., Japan. An input resistor 336 is connectedat one end to an input terminal 335a of the comparator 335 and at the other end to a movable arm of a variable resistor 337. The variable resistor 337 is connected across input terminals 333 and 334 of the comparison circuit 1330. A resistor 338 is connected at one end to a movable arm of a variable resistor 339 and at the other end to an input terminal 335b of the comparator 335. The variable resistor 339 is connected at one end to an input terminal 332 of the comparison circuit 1330 and is grounded at the other end. Terminals 3350, 335d, and 335a of the comparator 335 connect the comparator 335 to the positive terminal of a power source (designated in the drawing as +VC), to the ground and to the negative terminal of the power source (designated in the drawing as VC), respectively. An NPN transistor 341 has its emitter grounded, and its base connected to one end of a resistor 342 and to a collector of another NPN transistor 344. The other end of the resistor 342 is connected to a voltage source designated in the drawing as VC. The base of the transistor 344 is connected to an output lead 331 of the comparator 335 through a resistor 345, while the emitter of the same transistor is grounded. A collector of the transistor 341 is connected to the input terminal 334. An end of a variable resistor 343 is connected to the input terminal 334, while the other end of the same resistor is grounded. As clearly seen from FIG. 11, the transistors 34] and 344, the resistors 342 and 345, the variable resistor 343, and the voltage source VC constitute the 1-2 shift feedback circuit. The members recited in the above description of the l-2 shift circuit, except the members recited as those the l2 shift comparison circuit 1330.

- In operation, assuming that no voltage appears on -.the output lead 331 when no signal is applied to the input terminals 332, 333, and 334, the transistor 344 of the feedback circuit 1340 is nonconducting, accordingly the transistor 341 being conducting, thus the input; terminal 334 of thecomparison circuit 1330 is groundedf'Whe'n one vof the throttle voltages Ei E E ,-E L, and-12, which is picked according to the throttle angle and is hereinafter designated as E and the vehicle-speed voltage E,, are applied to the respec- .tive'input terminals 332 and 333 of the comparisoncircuit 1330, a voltage E appears "at the movablearm of the variable resistor 337, and another voltage E appears' at the movable arm of the variable resistor 339.

The voltages E and Em are given by the following formulas respectively? 1 where R,, is the resistance between the input terminal 333and the movable arm of the variable resistor 337, and R is the resistance between the movable arm of the variable 'resistor' 337 andthe collector of the transistor 341 in the feedback circuit 1340; and

where R is the resistance between the movable arm of the variable resistor 339 and the input terminal 332,

and R is the resistance between the movable arm of the variable resistor 339 and the ground.

'Th'e voltage E," is appliedtothe terminal 335a through'the resistor 336, and the voltage E is applied of the 1-2 feedback circuit in the above, all constitute to the te rminal-335b through 'therresistor 33s. The

comparator 335 compares E,,' with E When E,,' r-

' E 'ispositive or zero, and output voltage is delivered from the comparator 335 to the lead 331, while'no outjput voltage is delivered from the comparator 335 when E,,"' Ej 'is negative. Since the variable resistors 337 and 339 may be so adjusted that v i A (constant) thereby to give the relation:

Consequently, -comparison of E,,' with E whether E,,' E ispositive or zero, or negative is equivalent to the comparison of E, with AE whether E AE is positive orzero, or negative. The resistors 336 and 338 are protective resistors which protect the comparator 335 from large inputs that may be applied to the input terminals. I

When the output voltage appears in the output lead v 331 of the comparator 335 (the output lead 331 also --being the output lead of the comparison circuit 1330) dueto' E, EN,-'" 0,that is, E, AE z 0, a base current is supplied to the base of the transistor 344 through the resistor 345 in the feedback circuit 1340 to I 12 s make the transistor 344 conducting and accordingly to make the-transistor 341 nonconducting. Consequently,

assuming that the resistance of the variable resistor 343v is R vthe potential at the movablearm' of the variable resistor 337 is given. by the following formula: f

= i s/(R R, +R; 1-;E,.*

where E,," f potential at the movable. arm of the variable resistor 337 when the output voltage appears in the 5 output lead 3310f the comparison circuit 1330. Nowthat the input voltage at the input terminal 335a 'is changed from E,, to E,," as "above, the comparator 335 compares E, with E i whether E E,,. is positive or zero, or negative. When E, E isstill positive or zero, that is, E,,'' -E a O, the output voltage continues to be delivered from the comparator. If E,,"f E becomes negative, that is,'E,, E 0, the comparator 335 ceases to deliver the output voltage. Since n"n" E [(R, +R /R,', +,R,+R,) E [R /(R v H m if the variable resistors are adjusted to give I Die v Ra'l R0 while maintaining the previously established relation:

=A' (constant) Referring to FIG. 5, when the output voltage is delivered from the comparator 335,-this output voltage is-amplified by an amplifier 1350 to. energize the 1-2 shift solenoid 1280. When the l2 shift solenoid becomes energized, the 1-2 shift occurs as previously mentioned. When the comparator ceases to deliver the output, the l -2shift-solenoid becomes de energized.

Thereupon the 12 ,downshift occurs as previously mentioned. y I

The amplifier 1350 is of a conventional type, and its sole function is to amplify the output voltage from the comparator so that the output voltage can satisfactorily energize the l2 shift solenoid 1280. The amplifier 1350 is not necessary when the output voltage can satisfactorily energizethe solenoid. Thesolen oid 1280 is also of a conventional type. From the foregoing, it is apparent that AE 'is a l2 upshift point, and that A'E is a l2 downshift point, where AE A E if we let the suffix iofEN represent numerals l, 2, 3, 4, and 5, E coupled with -(i= 1, 2, 3, 4, and represent a group of throttle voltages consisting of E E E E and E Let the l-2 upshift point under a given E be designated as E Then all l-2 upshift points are given by the following formula:

mu-2) N. (i= 2. a d

Similarly, all l-2 downshift points are given by riri(1-2) 1Vi s where EM l-2 downshift point under a given and e l+ e u'i lfi' o =B' (constant) 7 wherein B B A A. Consequently, 2-3 upshift points and 2-3 downshift points are given by the following formulas: E i 3 BEA" l, 2, 3, 4, and where E,,,,, =2-3 upshift point under a given E E,,,,-,, '=BE (i=1, 2, 3,4, and 5) where E,,,, 2-3 downshift point under a given When E, E,,,,, while E, is increasing from a 'value smaller than E an output voltage is delivered from the 2-3 comparison circuit 1430. The output voltage is amplified by an amplifier 1450 for energizing the 2-3 shift solenoid l300to cause a 2-3 upshift. When E,,- E while E,, r is decreasing from a value greater than E,,,,,-,. the comparison circuit 1430 ceases to deliver the output voltage, thereupon causing de-energization of the solenoid 1300. Thereupon a 2-3 downshift occurs as previously described. The amplifier 1450 and the solenoid 1300 are of the same type as the amplifier 1350 and the solenoid 1280, respectivel In I IG. 7 the 1-2 upshift and downshift points, and the 2-3 upshift and downshift points are shown. Each group of shift points is connected by a phantom line.

The four phantom lines in FIG. 7 are drawn to shown that A, A, B, and B are constants.

When E,, A'E the transmission is definitely in the first gear range. When E,, is increasing from a value smaller than A 'E under given E and becomes AE E, AE the transmission is still in the first gear range. Only when E, AE does the upshift occur.

On the contrary, when E, is decreasing from a value greater than AE and becomes AE E,, AE the transmission is still in the second gear range. Only when E,, AE does downshift occur. Thus the range defined by A'E E,, AE is a l-2 shift hysteresis range along the vehicle speed voltage axis. a

Similarly, the range defined by BE g E,, BE is a 2-3 shift hysteresis range along the vehicle speed voltage axis. These hysteresis ranges are provided for the prevention of oscillation between adjacent gear ranges due to the change of the vehicle speed voltage.

When the multicontact switch is used to generate the throttle voltage, and, further, when the moving contact of the multicontact switch touches on one of the sta tionary contacts of the multicontact switch, for exam ple, the first contact, the throttle voltage changes from E to E suddenly, and when the moving contact detaches from the first contact, the throttle voltage suddenly changes from E to E if the throttle angle remains near the angle at which the moving contact touches the first contact, oscillation between the throttle voltages (in this case between E and E easily occurs due to touching and detaching of the moving contact on and from the first contact caused by vibrations of the moving contact and the stationary contact transmitted from the vehicle body, the vehicle engine, or the drivers leg. If E remains in the region defined by AE E,, A'E and the shift from the second gear range to the first gear range occurs when the throttle voltage changes from E to E and the shift from the first gear range to the second gear range occurs when the throttle voltage changes from E to E Therefore, the shift oscillation between the first and the second gear ranges occurs, when (1) AE g E,, A'E and (2) the throttle voltage oscillation between E and E occurs due to touching and detaching of the moving contact on and from the first contact (l) and (2) must occur at the same time This kind. of shift oscillation occurs when the following two conditions are met at the same time: (1) E, remains in the regions defined by AE,,,, g E,, A'E or in the regions defined by BE E BE (i l, 2, 3, and 4) and (2) the throttle voltage oscillation between adjacent throttle voltages occurs. In other regions, even if E, maintains its value at nearly the same value while the throttle voltage oscillation occurs, shifts do not occur successively. This is because the hysteresis ranges provided by the judge circuit for prevention of the shift oscillation caused by the change of the vehicle speed voltage prevent the occurrence of successive shifts. For example, if (1) E remains in the region: A'E E,, AE (2) the throttle voltage oscillation occurs between E and E starting from E and (3) the initial conditions are: the throttle voltage is at first E and the transmission is at first in the second gear range, then the shift occurs from the second gear range to the first gear range when the throttle voltage changes from E to E but the upshift from the first gear range to the second gear range does not occur when the throttle voltage changes from E to E Therefore, in this case the shift occurs only once, even if the throttle voltage oscillation between E and E continuously occurs.

if the throttle voltage generating circuit including the switch device of this invention is used to generate the throttle voltage, the throttle voltage oscillation never occurs due to the hysteretic characteristic of the reed switches even if the throttle angle hovers around each of the predetermined throttle angles corresponding to the positions of the reed switches. Therefore, the shift oscillation occurs in no region when the throttle volt- ,agegenerating circuit including the switch device of I this invention is used instead of the throttle voltage generating circuitincludingthe multicontact switch in the electricalcontrol circuitflto generate the throttle voltage, becauseone of the two requisite conditions for causing the shift oscillation, that is, the occurrence of the throttle voltage oscillation, is never met by the throttle voltage generating circuit including the switch device of this invention: I

- Thismatter-is'explained in anotherway by using a shift pattern diagram in terms of the .vehicle speed and the throttle angle below.

I f lf the vehicle speedV and the throttle angle O are angle as shown inFIG. 8. As shown in FIG. 8, due to' the hysteretic characteristic of the reedv switches the spaces along the throttle angle axis between the upshift lines and the downshift lines appear between 0 and 0 between (i and 0 between 6 and 0 and between 0 and 0 When the vehicle speed is maintained at nearly the same speed, an upshift occurs when the throttle angle isdecreasing. Therefore, the upshift lines which are perpendicular to the throttle angleaxis are located at 0 0 0 and 0,". Similarly, the downshift lin'es perpendicular to the throttle angle axis are located at 6,, 6 0 and 0,, because the downshift occurs only when the throttle angle is increasing if the vehicle speed ismaintained at nearly the same speed. In

other words, hysteresis'of the reed switches lowers the upshift lines perpendicular to the throttle. angle axis by the size of hysteresis of the reed switches. If hysteresis j of the switch device does not exist, asis the case with the,multicontact switch, the spaces along the throttle angle axisbet'ween the upshift lines-and the downshift lines do not exist, and the upshift lines and downshift lines perpendicular to the throttle angle axis are located at the same correspondingthrottle angles: 0,, 0 "0 and 0 The spaces along the throttle angle axis between the upshift line's'and the downshift lines mean hysteresis between the upshift and the downshift when the-vehicle speed is maintained at nearly the same speed thereby preventing oscillation betweengear ranges. Therefore, these spaces are hysteresis ranges.

v As shown in FIG. 8, the hysteresis ranges, which represent two gear ranges according to the history of the gear ranges, intervene continuously and entirely between the adjacent gear ra e regions each of which pattern consists of stepped shift lines can be done without using the switch device of this invention by providing one group of throttle voltages for the upshifts and another group of throttle voltages for the Y downshifts in an electricalcontrol circuit for a transv mission in contradistinction to the electrical control nln circuit of this invention which uses the same group of throttle voltages for the upshifts and the downshift. However, it is clear that an electrical controlcircuit for. a transmission which uses two different groups of throt tle voltages each provided for the upshifts and for'the downshifts must have farm'ore complicated electronic circuits than the electrical control circuit of this invention. Therefore, one advantage of the electrical control circuit including. the. switch device of this invention (theelectrical control circuitof this invention) is that the electrical control circuit of this invention, notwithstanding 'thesimplicity of structure thereof, always performs stable, shifts however the throttle angle and the vehicle speed may change. i 7

Another characteristic of the electrical control circuit of this invention is, in the shift pattern diagram in terms of .vehicle speed and throttle angle, the separation of each line parallel to the throttle angle axis of the 1-2 and 2-3 upshift lines and the 1-2 and 2-3 downshift lines into two different kinds of branches in i the regions between 0 and 0,, between 0 and'ti between d and 0 and between 0 and 0 v This is described in detail below. r Referring to FIG; 8, the 1-2 upshift line which is designated'as V ,f (0) in the drawing consists of A -A,,,, and B,-B between 6, and0 A A and B -B between 0 and 0,, A 'A and B 'B between I vehicle speed is increasing via the routes as shown by 0 and 0 and 'A -A and B.,Bj between 0., and 6 These separations occur'due to the existence of two different conditions of each applicable reed switch: one condition in which that particular reed switch 'is' on, and another in which that particular reed switch is off.

Taking the case of the regionbetweeh 0 and 0 ,'the two branches of the upshift lines are described below.

When the throttle angle stays between 9 and 0 after decreasing. from an angle bigger than 0 (there-' fore, the reed switch 5 is on, and, of course all reed switches whose corresponding throttle angles. for posi tioning thereof 'are smaller than the corresponding throttle angle of the reed switch 5 are also on) and the two arrows designated as a in FIG. 8', the upshift occurs at the shift line of A A I t v U When the throttleangle stays between 6 "and0 after increasing from an angle smaller than 9 (therefore, the reed switch 5 is off, butthe reed switches 4 and 3 are on) and the vehicle speed is increasing via the routes as shown by two arrows designated as b in FIG. 8, the upshift occurs at the shift line 8 -3 Similarly, taking the case of the region between 0 and 0 the two branches of the downshift line are described below. I a

When the throttle angle stays between 0., and 0 after decreasing from an angle bigger than 0 (there- I fore, the reed switch 6 and other reedswitches whose corresponding throttle angles for positioning thereof are smaller than the corresponding throttle angle of the reed switch 6 are on) and the vehicle speed is decreasing via the routes as shown by two arrows designatedas c in FIG. 8, thedownshift occurs at the shift line of r m e When the throttleangle stays between 0,' andv 6 after increasing from an angle smaller than 0 (there'- fore, the reed switch ,6 is off, butother reed switches whose corresponding throttle angles for positioning thereof are smaller than the corresponding throttle angle of the reed switch 6 are on) and the vehicle speed is decreasing via the routes as shown by two arrows designated as d in FIG. 8, the downshift occurs at the shift line of D,-D

lf hysteresis of the switch device does not exist, as is the case with the multicontact switch, all the l-2 upshifts and 1-2 downshifts in the region between 0, and. between 0 "and 0 between 0 and 6 and between 6 and 0,, occur at the lines of B,B,, 8 -8 10 8 -8 and B B only, and at the lines of D D,',

. The same description as made for-the 1-2 upshiftline V f,' ((9 and the l-Zdownshift line V=f,(0) is apt plied to the 2-3 upshift line designated as V-'---f (0) in FIG. 8 and the 2- 3 downshift line designated as V =f (0) in the same drawing.

For clarification, domains of the control and the v electrical control circuit are defined below. i

A three forward speedtransmission controlled by the control of this invention comprises a torque converter, aplanetary gear set, a transmission output shaft, and the control, wherein the control comprises an electrical control'circuit, two hydraulic shift valves, two clutches,

and two brakes, wherein the electrical control circuit comprises a throttle position signal generator, a vehicle speed signal generator, two solenoids, and'two shift judge circuits comprising two comparison circuits and two feedback circuits.

It is claimed:

generating a throttle signal which is a function of throttle position; means for generating a speed signal which is a function of vehicle speed;'and first circuit means (1) connected with said throttle signal generating means and speed signal generating means to receive said signals therefrom, and (2) operatively connected 40 to said solenoid for effecting operation thereof; said first circuit means including means for comparing said signals and producing an output when said signals attain a predetermined relationship; the improvement wherein said throttle signal generating means comprises, in combination: magnetic means connected to said throttle means; second circuit means having a supply terminal connected with said first circuit means for generating a step voltage which represents said throttle signal, said. second circuit means including a plurality of reed switches mounted on a supporting body in spaced relation to each other and to said magnetic means; said reed switches being energized by said "III magnetic means; wherein said step voltage changes in a stepped manner when'anyof said reed switches is closed, said step voltage being supplied to said first circuit means through said supply terminal.

' 2. A control as recited in claim 1, wherein each of said switch means has apredetermined angle assigned thereto, each of said switch means being disposed relativeto said magnetic means so as to be energized when a throttle angle as measured from a fully closed position of said throttle means becomes said predetermined i A control as recited in claim 2, wherein said magnetic means isdesigned so as to energize all ofsaid switch means whose said predetermined angles are smaller than said throttle angle.

4. Acontrol as recited in claim 3, wherein each of said switch means is de-energized when said throttle angle becomes an angle smaller than said predetermined angle assigned to each of said switch means.

5. A control as recited in claim 3, wherein said magnetic means comprises: a rotatable disc operatively connected to said throttle means; and a magnet mounted on said disc.

6. A control as recited in claim 3, wherein said second circuit means further comprises: a plurality of impedance elements each of which is connected in series with each one of said switch means to make a set of series combinations of one of said switch means and one of said impedance elements; an additional impedance element; and a source of electrical energy each of said series combinations being connected in parallel with other of said series combinations to make a parallel combination; one terminal of said parallel combination being connected to one terminal of said electrical energy source, a second terminal of said parallel combination being connected with one terminal of said additional impedance element, a second terminal of said additional impedance element being connected to a second terminal of said electrical energy source; said supply terminal being connected with said parallel combination second terminal.

7. A control as recited in claim 6, further comprising a further impedance element connected across said parallel combination.

8. A control as recited in claim 6, wherein each of said switch means is de-energized when said throttle angle becomes an angle smaller than said predetermined angle assigned to each of said switch means.

9. A controlas recited in claim 7, wherein each of said switch means is de-energized when said throttle angle becomes an angle smaller than said predetermined angle assigned to each of said switch means. 

1. In a control for an automatic transmission driven by an engine having throttle means, comprising, in combination: ratio changing means; a solenoid for operating said ratio changing means; means for generating a throttle signal which is a function of throttle position; means for generating a speed signal which is a function of vehicle speed; and first circuit means (1) connected with said throttle signal generating means and speed signal generating means to receive said signals therefrom, and (2) operatively connected to said solenoid for effecting operation thereof; said first circuit means including means for comparing said signals and producing an output when said signals attain a predetermined relationship; the improvement wherein said throttle signal generating means comprises, in combination: magnetic means connected to said throttle means; second circuit means having a supply terminal connected with said first circuit means for generating a step voltage which represents said throttle signal, said second circuit means including a plurality of reed switches mounted on a supporting body in spaced relation to each other and to said magnetic means; said reed switches being energized by said magnetic means; wherein said step voltage changes in a stepped manner when any of said reed switches is closed, said step voltage being supplied to said first circuit means through said supply terminal.
 2. A control as recited in claim 1, wherein each of said switch means has a predetermined angle assigned thereto, each of said switch means being disposed relative to said magnetic means so as to be energized when a throttle angle as measured from a fully closed position of said throttle means becomes said predetermined angle.
 3. A control as recited in claim 2, wherein said magnetic means is designed so as to energize all of said switch means whose said predetermined angles are smaller than said throttle angle.
 4. A control as recited in claim 3, wherein each of said switch means is de-energized when said throttle angle becomes an angle smaller than said predetermined angle assigned to each of said switch means.
 5. A control as recited in claim 3, wherein said magnetic means comprises: a rotatable disc operatively connected to said throttle means; and a magnet mounted on said disc.
 6. A control as recited in claim 3, wherein said second circuit means further comprises: a plurality of impedance elements each of which is connected in series with each one of said switch means to make a set of series combinations of one of said switch means and one of said impedance elements; an additional impedance element; and a source of electrical energy each of said series combinations being connected in parallel with other of said series combinations to make a parallel combination; one terminal of said parallel combination being connected to one terminal of said electrical energy source, a second terminal of said parallel combination being connected with one terminal of said additional impedance element, a second terminal of said additional impedance element being connected to a second terminal of said electrical energy source; said supply terminal being connected with said parallel combination second terminal.
 7. A control as recited in claim 6, further comprising a further impedance element connected across said parallel combination.
 8. A control as recited in claim 6, wherein each of said switch means is de-energized when said throttle angle becomes an angle smaller than said predetermined angle assigned to each of said switch means.
 9. A control as recited in claim 7, wherein each of said switch means is de-energized when said throttle angle becomes an angle smaller than said predetermined angle assigned to each of said switch means. 